[luatex] accessing attribute registers (and other register types)

[Hans Hagen]

On 6/16/2015 10:26 PM, David Carlisle wrote:
> If you have an attributedef token defined via
>
> \attributedef\qqq=301
> \qqq=53
>
> (or some allocation macro that does that internally)
>
> then you can access the value (53 here) from lua as tex.attribute.qqq
>
>
> but to use in node callbacks with such as
>
>   node.has_attribute(n, attr_number)
>
> then you need access to the underlying register number (301).
>
> Does luatex have a documented way to get from the csname "qqq"
> to the register number?
>
> The latex luatexbase package achieves this by wrapping the \attributedef
> in a call to \directlua that stores the "qqq"->53 association in its
> own lua table.
>
> It seemed to me that luatex must have this information and it ought to be
> possible to simplify this just to do a bare \attributedef.
>
> The following code appears to work producing
>
> qqq is attribute: 301 value: 53
>
> hhhz is attribute: 444 value: 99
>
> zzz is count: 200 value: 2
>
> that is the register number and value in each case, but poking into
> tex.hashtokens seems like it probably is not the correct thing to do
> and I'm not sure I'm supposed to assume that all the countdef tokens
> get consecutive identifying integers?
>
>
>
> \attributedef\attrzero=0
>
> \countdef\zzz=200
> \zzz=2
> \def\zz{}
> \attributedef\qqq=301
> \qqq=53
> \def\hmm{lll}
>
> \attributedef\hhhz=444
> \hhhz=99
>
>
> \directlua{
> texio.write_nl("")
>
> v=tex.hashtokens()["qqq"][2] - tex.hashtokens()["attrzero"][2]
> texio.write_nl("qqq is attribute: "  .. v .. " value: " .. tex.attribute["qqq"])
>
>
> v=tex.hashtokens()["hhhz"][2] -tex.hashtokens()["attrzero"][2]
> texio.write_nl("hhhz is attribute: "  .. v .. " value: " ..
> tex.attribute["hhhz"])
>
>
> v=tex.hashtokens()["zzz"][2] -tex.hashtokens()["pageno"][2]
> texio.write_nl("zzz is count: "  .. v.. " value: " .. tex.count["zzz"])
>
>
> texio.write_nl("")}
>
> \bye

\attributedef\zeroattribute=0
\attributedef\bar=999

\directlua {
     function attributenumber(name)
         local n = newtoken.create(name).mode - 
newtoken.create("zeroattribute").mode
         if n >= 0 then
             return n
         else
             return false
         end
     end
}

\directlua{print(attributenumber("crap"))}
\directlua{print(attributenumber("bar"))}
\directlua{print(attributenumber("10>color"))}
\directlua{print(attributenumber("10>colormodel"))}

Hans

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                                           Hans Hagen | PRAGMA ADE
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